The present invention relates to a micro flowguide device, especially to a configurable/programmable micro flowguide device provided with electrolytic bubble actuator. The micro flowguide device of this invention may be used in a variety of medical, chemical, environmental, electronic, pharmaceutical, agricultural or military microfluidic applications.
In the field of the miniaturized microfluidic device, flow control components with no-moving-parts elements play a significant role in simplifying the device fabrication/operation complexity and reducing mechanical wear/reliability problems. Among them, micro flowguides, which guide flow to a predefined route, are useful in many microfluidic applications including cell manipulation, particle sorting, drug delivery, and extraction/mixing of (bio)chemical samples . . . etc. Disclosed in the prior arts, mechanisms for micro moving-parts (or no-moving-parts) flow control components include:
1. Thermally actuated flow branching: Non-uniform heating a moving fluid causes a variation of viscosity of fluid across the channel section, and hence an asymmetric flow velocity profile across the channel. A flow can then be directed toward the branch channel along the side of lower velocity profile.
2. Thermal bubble valve: Locally heating a moving fluid to its boiling point generates localized steam bubbles. Bubbles, which are usually carried downstream and constrained at a converged channel, will cause discontinued streamlines and reduce flow velocity and thus act as a valve.
3. Magneto-hydrodynamic (MHD) flow: Applying a magnetic field to a flow carrying moving electric charges generates a driving force to move the fluid to a direction defined by the cross-product of moving charges and the magnetic field. (Electrokinetic flow is another similar principle used to direct flow toward predefined electrical field.)
4. Thermal gelatin valve: A ball valve operating according to the volumetric expansion or contraction of a temperature sensitive gelatin that acts as the ball of the valve.
5. Electrolysis-bubble actuated gate valve: A flow valve consisting a laterally moving piston that serves as the ball of a valve. The piston is actuated by 2-state buckling deformation of tether beams connected to it. Electrolytic bubbles will generate small push force on the buckling beams and larger buckling deformation will snap the piston to the desired position into the flow channel and close the valve.
6. Mechanically driven valves: Valve driven directly by mechanical force and structures.
In the aforementioned arts, the thermal gelatin valve, the electrolysis-bubble actuated gate valve and the mechanically driven valves are prepared with special actuation materials or are provided with internal or external moveable parts to control a flow inside a micro channel. This does not only increase the number of working elements/components and their required space to control a flow in a micro channel but also makes the high-density integration of such components and external system more complicated. Flow control using thermally actuated flow branching, thermal bubble valve, and the magneto-hydrodynamic flow are able to provide a simpler, self-embedded and no-moving-parts mechanisms. However, the operational temperature or the operational voltages (or currents) of these arts may be inapplicable to some (bio)chemical liquid or reagents.
Many development efforts have been dedicated to microfluidic array device in which fluids are delivered according to pre-defined flow rates and directions through series of steps to complete necessary (bio)chemical reactions. On the microfluidic array device, micro channels or micro conduits can only passively link in parallel or in series multiple reactions each of which requires its own microfluidic components to complete specific task. In contrast to these functional-specific components, flowguide becomes a general multiplexing component to provide an active conducting of fluids in an integrated microfluidic conduit network. Therefore it becomes very desirable in a microfluidic array device to have active control over fluid conducting, flow rate, and dwelling time (or charging time) . . . etc in order to improve device controllability, application flexibility and reactive process accuracy.
It is thus desired to have a novel and simple micro flowguide preferably with no-moving-part elements to maintain cost effectiveness of a usually disposable/or portable microfluidic device.
It is also desired to have a novel micro flowguide capable of active multiplexing flows without extra needs of using other complicated external actuation mechanisms.
It is also desired to have a novel micro flowguide where the operational mechanism will be compatible to the reactions performed inside the microfluidic array device.
It is also desired to have a small and inexpensive micro flowguide that is capable of being flexibly integrated at high density into a microfluidic array device.
It is also desired to have a configurable/programmable micro flowguide in order to enhance overall flow control flexibility and reaction accuracy in an integrated microfluidic conduit network.
It is also desired to provide an easy access to activate a micro flowguide for a software man-machine interface.
One objective of this invention is to provide a novel micro flowguide with no-moving-part working elements/components to simplify miniaturized fabrication process and to save its concomitant cost.
Another objective of this invention is to provide a novel micro flowguide with a simple and independent mechanism to actively define the ON/OFF states of a microfluidic conduit branch.
Another objective of this invention is to provide a micro flowguide that can work on DC source at low power consumption.
Another objective of this invention is to provide a novel micro flowguide where the operational mechanism will be confined locally and generally compatible to required reactions to be performed in a microfluidic array device.
Another objective of this invention is to provide a low-cost and simple micro flowguide device for high-density integration into a microfluidic array device.
Another objective of this invention is to provide a micro flowguide which function can be configured to formulate a desired routing of flows through micro conduit branches or defined in a timeline by software interface in order to provide special fluid conducting sequences.
A xe2x80x9cflowguidexe2x80x9d is hereby defined as a component/device that can direct a conduit flow to the predefined paths. When multiple paths are simultaneously available for a single upstream flow, a flowguide opens a connection for this upstream flow to a desired downstream flow path. In another word, the undesired connections must be closed to avoid too much cross talk. When there are only 2 downstream choices available, the flowguide acts like a flip-flop device that provides one of the 2 output states for the upstream flow signal. Therefore the flowguide could be considered a switch or a logic device in an analogy to those used in logic circuit or optical communication.
Explained by this invention, a configurable/programmable micro flowguide adopts the principle of micro electrolytic bubble actuator as its working mechanism to activate the On/Off State of a micro conduit branch over which the micro flowguide straddles. The On state defines the availability of the micro conduit branch to transfer fluids while the Off state defines the unavailability of the micro conduit branch to transfer fluids.
When an electrical logic signal connected to the micro flowguide""s accompanying DC power relay maintains at low/high level, the DC source will be disconnected/connected to the micro flowguide respectively to turn On/Off the micro conduit branch. In order to implement high-density distribution of such a micro flowguide into a micro conduit network, this micro flowguide is designed without moving-part elements so that less space and simpler fabrication process are required.
The electrolytic bubbles are generated through a localized electrolytic reaction. The exposure of a set of DC-source-connected electrodes inside a conduit branch is used to enable a local electrolysis and to generate gas bubbles. Accumulated bubbles will be trapped and kept at several corner traps, in principle, like a water hammer absorption air reservoir, of the invented flowguide. When the backward pressure of trapped bubbles is rising to the level of forward pressure head, flow speed reduces to zero and channel branch is shut down. Typical shutdown response time for the invented flowguide design is about 1xcx9c2 seconds. By enabling the Off state of channel branches, only channels with On state will be available to conduct channel fluids through a micro fluidic conduit network of a microfluidic array device.
Appropriate placement of such a flowguide in a microfluidic channel network can be used to configure a user-defined route that links inlet, network nodes where pre-defined (bio)chemical actions are held in a timeline, and the final outlet, making such a device platform configurable for different applications and fluid conducting sequences.